With improvement of human requirements for an intelligent life, a requirement for data processing is increasing. Global energy consumption on data processing reaches hundreds of billions of KWH or even trillions of KWH every year. And a large-scale data center covers an area of ten thousands of square meters. Therefore, key indicators for sound development of this industry include high efficiency, high power density and high reliability.
A key element of a data center is a server whose mainboard generally comprises data processing chips such as a CPU, Chipsets, and a Memory, a power supply and requisite peripheral components. FIG. 1 is a schematic diagram of a mainboard power supply. As shown in FIG. 1, the cascade mainboard power supply at different stages on a mainboard receives an input of a power bus and converts it into different outputs so as to provide it for various loads. For example, as shown in FIG. 1, the mainboard power supply receives an input of 400V and converts it into a first output (e.g., 48V) by means of a first-stage converter circuit (400V-48V in FIG. 1). A second-stage converter circuit (e.g., 48V-12V and 48V-Vo in FIG. 1) cascaded with the first-stage converter circuit receives the first output and converts it into a second output, and directly provides the second output for different loads (e.g., a hard disc or a fan, etc.) according to the value of the second output. Or, the second output may be further converted into a third output by means of a third stage circuit (e.g., 12V-Vo) so as to provide it for the corresponding loads.
The mainboard power supply and loads may be subject to test in order to ensure their stability and reliability. FIG. 2 is a schematic diagram of a test system of the mainboard as shown in a conventional test in FIG. 1. As shown in FIG. 2, the equipment under test (E.U.T.) generally comprises a main circuit and a control circuit, and is configured to receive an input signal from a test power supply and provide an output to a load. The test control circuit is configured to send a control signal for controlling the E.U.T. Within a normal operating range of a load, the E.U.T. (e.g., it is converter circuits at different stages on a mainboard) needs to provide a certain corresponding output. In addition, the converter circuit should provide an output with wider range than the normal operating range in order to test the stability of different kinds of load and the whole mainboard power supply. For example, supposing an output Vo of the third stage circuit (12V-Vo) as shown in FIG. 1 is 5V. Typically, the normal output voltage range is 5±5% V. In addition, generally the circuit voltage output range should be 5±15% V (for example) in order to test the stability of a load under different voltages. Thus, the output range of a circuit in the test state is much wider than the range in its normal operating state, i.e., as to the same input range, the gain range in the test state is much wider than the gain range in the normal operating state. It is unavoidable to sacrifice normal operating efficiency in order to ensure normal operation of a circuit in the test state. This is because the wider the gain range is, the lower the circuit efficiency is. Or extra means (e.g., more complex circuit structures, etc.) are required for acquiring higher circuit efficiency in the normal operation.